That doesnt mean the 10th powerplay is obligated to give you a goal. Each PP is its own independent event.
http://www.wyzant.com/help/math/stat...in_probability
Quote:
When two events are said to be independent of each other, what this means is that the probability that one event occurs in no way affects the probability of the other event occurring. An example of two independent events is as follows; say you rolled a die and flipped a coin. The probability of getting any number face on the die in no way influences the probability of getting a head or a tail on the coin.

Because you fail on one power play, it does NOT mean the chances are better the next. At all.